I. Field of the Invention
The present invention relates generally to the field of catheter-based tissue ablation devices and techniques and, more particularly, to systems for ablation to relieve atrial cardiac arrhythmias. Specifically, the invention relates to curing atrial fibrillation by using transcutaneous transvascular catheter ablation to recreate the effect of the Cox Maze surgical procedure.
II. Related Art
Cardiac arrhythmias, particularly atrial fibrillation, are common and dangerous medical conditions causing abnormal, erratic cardiac function. Atrial fibrillation is observed particularly in elderly patients and results from abnormal conduction and automaticity in regions of cardiac tissue. Chronic atrial fibrillation (AF) may lead to serious conditions including stroke, heart failure, fatigue and palpitations. The treatment of chronic AF requires the creation of a number of transmural contiguous linear lesions. The use of a pattern of surgical incisions and thus surgical scars to block abnormal electrical circuits, known as the Cox Maze procedure, has become the standard procedure for effective surgical cure of AF. The procedure requires a series of full-thickness incisions to isolate the pulmonary veins and the posterior wall of the left atria. Additional lines involve the creation of lesions from the posterior wall to the mitral valve, at the atrial isthmus line and superior vena cava (SVC) to the inferior vena cava (IVC) with a connection to the right atrial appendage.
Catheters have been developed that make the corrective procedure less invasive. They are designed to create lesions by ablation of tissue that performs the function of the surgical incisions. These include catheters that attempt to connect a series of local or spot lesions made using single electrodes into linear lesions. Devices that use a linear array of spaced electrodes or electrodes that extend along the length of a catheter have also been proposed.
More recently, technologies regarding cryogenic and radio frequency (RF) balloon devices in addition to loop type multi-electrode catheter devices have been proposed for the isolation of the pulmonary veins (PV). It has been found that isolation of the PVs can be achieved consistently with a PV cryogenic balloon device now in clinical trials. However, presently no technology has been shown to consistently and safely create effective transmural contiguous lesions that exhibit an effectiveness that rivals the surgical cuts placed in the Cox Maze.
Important drawbacks found fundamental in the current approaches can be attributed to several factors including a lack of consistent contact between the ablation devices and the target tissues, an inability to define lesion maturation and the inability to connect lesions in a manner so as to create a continuous transmural line that produces an electrical conduction block.